Method for the arrangement of impingement cooling holes and effusion holes in a combustion chamber wall of a gas turbine

ABSTRACT

A method for the arrangement of effusion holes and impingement cooling holes in a combustion chamber wall including: distribution of the effusion holes in the surface to be cooled in accordance with pattern, diameter and dimension selections made; distribution of the impingement cooling holes in accordance with pattern, diameter and dimension selections made; checking of the number of matches and their spacing from one another, taking into account the component and assembly tolerances; comparison with the permitted number and their minimum spacing; and, if quality requirements are not met, taking corrective actions, including selecting alternative diameters and patterns.

This application claims priority to German Patent ApplicationDE102012025375.3 filed Dec. 27, 2012, the entirety of which isincorporated by reference herein.

This invention relates to a method for the arrangement of effusion holesand impingement cooling holes in a combustion chamber wall of a gasturbine in accordance with the generic part of Claim 1. In detail, theinvention relates to the arrangement and mutual assignment of theeffusion holes and impingement cooling holes in the combustion chamberwail and in the combustion chamber tile fastened thereto. The inventionalso relates to a combustion chamber wall manufactured according to themethod.

it is known from the state of the art to provide the combustion chamberwall and the tile carrier, respectively, with impingement cooling holes.Cooling air is passed through these impingement cooling holes onto thesurface of the combustion chamber tile in order to cool it. Thecombustion chamber tile is cooled here by impingement cooling from thecold side of the combustion chamber tile. The combustion chamber tile isusually arranged at a distance from the combustion chamber wall, formingan interspace through which the cooling air exiting from the impingementcooling holes can move. In this way, that side of the combustion chambertile facing away from the inner volume of the combustion chamber andreferred to as the cold side is cooled.

By means of the effusion holes, cooling air flows through the combustionchamber tile and settles as a film onto the hot surface of thecombustion chamber tile in order to cool it and shield it from the hotcombustion gases.

WO 92/16798 A1 describes the design of a gas-turbine combustion chamberusing metallic tiles fastened by means of stud bolts, which due to thecombination of impingement and effusion cooling results in effectivecooling and hence permits a reduction in cooling air consumption. Thegeometric relationship of the impingement holes to the effusion holes isnot defined, and to each impingement cooling hole is assigned aneffusion hole.

U.S. Pat. No. 6,237,344 B1 describes a two-layer impingement/effusioncooling system using two metal sheets which are kept a defined distanceapart by bulges pressed in on the cold side. A 1:1 ratio of bulges andimpingement cooling holes is stipulated here, since the bulges areintended to protect the impingement cooling jets from crossflow in theimpingement cooling cavity. A geometric relationship between impingementholes and effusion holes is not described.

EP 1 104 871 81 describes the relationship of a large impingementcooling hole to a group of effusion holes, for example six effusionholes, equally spaced from a seventh, central effusion hole, where theimpingement cooling jet inside the group hits the effusion wall. Theimpingement cooling holes are arranged in offset rows so that an equaldistance from the surrounding impingement cooling holes is obtained andhence an equilateral triangle is formed between them, with one side ofthe triangle being aligned in the circumferential direction.

U.S. Pat. No. 5,758,504 A describes an impingement/effusion pattern inwhich the impingement cooling holes are arranged in equilateralrectangles on the combustion chamber wall, with a diagonal of the squarebeing aligned in the circumferential direction. The effusion holes arearranged relative to the impingement cooling holes according to variousprinciples (e.g. relative to the corners of the square, but not in themiddle).

The state of the art shows design principles of cooling hole patternswhich can be arranged in different ways and designs. For example,hopping patterns are known which can include two or more recesses. Thestate of the art also shows n-cornered basic cells, for exampletriangular or rectangular or square basic cells, where one side ordiagonal of the basic cell is usually aligned in the circumferentialdirection or axial direction of the combustion chamber (relative to acenter axis of the combustion chamber).

If the design does not specify a relationship of impingement holes andeffusion holes, it is then possible for impingement cooling jets todirectly match an effusion hole and therefore not impinge in the truesense on the combustion chamber wall, but flow off immediately throughthe effusion hole, so that no stagnation point forms on the combustionchamber wall. A high heat transfer at this point, and hence the superiorcooling effect, are thus not achieved.

If a fixed relationship between impingement jets and effusion jets isspecified in the design (e.g. the impingement cooling hole is alwayspositioned on the wall at a distance x upstream on the symmetry linesbetween the two effusion holes through which air flows off again), thenthe design and also the production quality must likewise permit this,otherwise there is still a risk of placing an impingement cooling holedirectly above an effusion hole and losing the impingement coolingeffect. Experience has shown, however, that the total of component andassembly tolerances makes it difficult to correctly position a largenumber of holes, given all the possible differences of the componentsfrom one another.

The object underlying the present invention is to provide a method forthe arrangement of effusion holes and impingement cooling holes, whichwhile being simply designed and easily applicable, ensures operationallysafe and dependable cooling of the combustion chamber tiles.

It is a particular object of the present invention to provide solutionto the above problematics by the combination of the features of Claim 1.

It is thus provided in accordance with the invention that the patternsof effusion holes and impingement cooling holes are selected and thenchecked as to whether their mutual assignment meets the requirements.This procedure can in particular also be conducted with the aid ofcomputers.

In accordance with the invention, a different ordering principle is usedfor the impingement cooling holes and for the effusion holes in such away that the possibility of an impingement cooling hole directlymatching an effusion hole is minimized, despite the component andassembly tolerances.

If an n-hopping pattern is used on the effusion side, such that thepattern is repeated after n rows or columns, then an m-sided basic cellis used on the impingement cooling side for distribution of theimpingement cooling holes in such a way that the probability of placingan impingement cooling hole directly above an effusion hole isminimized, taking into account all component and assembly tolerances.

A basic cell is defined here such that a cooling air hole is provided inevery corner of the basic cell.

The selected basic cell is then rotated in its edge length and in itsalignment relative to the axial direction and to the circumferentialdirection such that the probability of overlapping is minimized despitethe component and assembly tolerances. If the number of overlaps for theselected basic cell is still too high or if the matches are too closetogether, a basic cell with a higher or lower number of corners isselected and the optimization is repeated.

Axial direction is understood in accordance with the invention as beinga direction parallel to the center plane of the combustion chamber andhence along the direction of flow through the combustion chamber.

The same method in accordance with the invention can also be used for anarrangement of the effusion holes in an n-cornered basic pattern.

These considerations result, in accordance with the invention, in thefollowing method for determining the hole patterns for impingement holesand effusion holes, in which the input data from the cooling design, thetotal of the geometric surfaces of all effusion holes, the total of thesurfaces of all impingement cooling holes and the surface to be cooledare assumed to be known or given:

-   -   1.) Stipulation of the maximum permitted number of matches,        where an impingement cooling hole axis matches an effusion hole        center point at a distance y, and of the minimum spacing between        the matches.    -   2.) Selection of the pattern for the effusion holes.    -   3.) Stipulation of the diameter of the effusion holes.    -   4.) Calculation of the dimensions of the basic cell for the        effusion holes, such that all holes provided fit into the        surface to be cooled.    -   5.) Distribution of the effusion holes in the surface to be        cooled in accordance with the selections made under 2. and 3.    -   6.) Selection of the pattern for the impingement cooling holes.    -   7.) Stipulation of the diameter of the impingement cooling        holes.    -   8.) Calculation of the dimensions of the basic cell, such that        all impingement cooling holes provided fit into the surface to        be cooled.    -   9.) Selection of the alignment of the basic cell for the        impingement cooling holes.    -   10.) Distribution of the impingement cooling holes in accordance        with the selections made under 6. and 7.    -   11.) Checking of the number of matches and their spacing from        one another, taking into account the component and assembly        tolerances.    -   12.) Comparison with the permitted number and their minimum        spacing.    -   13.) If the quality requirements are not met:        -   a) First select another alignment of the basic cell of the            impingement cooling holes and return to 10.        -   b) If this does not succeed, chose another diameter of the            impingement cooling holes and return to 8.        -   c) If this does not succeed, chose another pattern and/or            another basic cell of the impingement cooling holes and            return to 6.        -   d) If this does not succeed, chose another effusion hole            diameter and return to 4.        -   e) If this does not succeed, chose another effusion hole            pattern and return to 3.        -   f) If this does not succeed, check the input data from the            total of the geometric surfaces of all effusion holes, the            total of the geometric surfaces of all impingement cooling            holes and the surface to be cooled.        -   g) If this does not succeed, change the quality            requirements.    -   14. When the quality requirements have been met, then the final        pattern has been found.

An advantageous and stable arrangement using the method in accordancewith the invention is also characterized in that the number of effusionholes is not an even-numbered multiple of the number of impingementcooling holes.

The method in accordance with the invention for selecting a non-relatedpattern between impingement holes and effusion holes can be applied toimpingement/effusion-cooled tiles, and also to other double-walledcooling arrangements, for example from two sheet metal layers.

While the specific search principle for the relationship of impingementcooling hole to effusion cooling hole does not completely rule out thatthe case may occur now and then of an impingement cooling hole blowingprecisely into an effusion hole so that no impingement cooling effect isachieved, the distance between such failures in impingement cooling ismaximized. It does not occur two times at directly adjacent points.

The impingement cooling effect is exploited to a high degree for widecomponent and assembly tolerances too, assuring a high cooling effectand as a result a long component service life. Due to the widetolerances, the component costs are lowered and nevertheless a sturdyproduct is obtained.

In a favourable development of the invention, it is furthermore providedthat at least on one part of the combustion chamber wall the impingementcooling holes are distributed according to a different rule than thatfor the effusion holes, where a fixed geometric relationship ofimpingement cooling holes and effusion holes is avoided.

The invention also relates to a combustion chamber wall designed usingthe method in accordance with the invention. It must be noted inparticular here that at least on one part of the combustion chamber wallthe impingement cooling holes are distributed according to a differentrule than that for the effusion holes, while avoiding a fixed geometricrelationship between the impingement cooling holes and the effusioncooling holes.

The present invention is described in the following in light of theaccompanying drawing, showing an exemplary embodiment. In the drawing,

FIG. 1 shows a schematic representation of a gas-turbine engine inaccordance with the present invention,

FIG. 2 shows a simplified schematic sectional view through a combustionchamber wall and combustion chamber tiles in accordance with the stateof the art,

FIG. 3 shows an example in accordance with the state of the art, wherethe impingement and effusion holes and the impingement cooling holes areassigned in accordance with the design requirement,

FIG. 4 shows an arrangement, by analogy with the representation of FIG.3, of the actual assignment of effusion holes and impingement coolingholes,

FIG. 5 shows an exemplary embodiment in accordance with the presentinvention of the design assignment by analogy with the representation ofFIG. 3, and

FIG. 6 shows a representation, by analogy with FIG. 4, of the solutionin accordance with the invention of the assignment of effusion holes andimpingement cooling holes.

The gas-turbine engine 10 in accordance with FIG. 1 is a generallyrepresented example of a turbomachine where the invention can be used.The engine 10 is of conventional design and includes in the flowdirection, one behind the other, an air inlet 11, a fan 12 rotatinginside a casing, an intermediate-pressure compressor 13, a high-pressurecompressor 14, a combustion chamber 15, a high-pressure turbine 16, anintermediate-pressure turbine 17 and a low-pressure turbine 18 as wellas an exhaust nozzle 19, all of which being arranged about a centerengine axis 1.

The intermediate-pressure compressor 13 and the high-pressure compressor14 each include several stages, of which each has an arrangementextending in the circumferential direction of fixed and stationary guidevanes 20, generally referred to as stator vanes and projecting radiallyinwards from the engine casing 21 in an annular flow duct through thecompressors 13, 14. The compressors furthermore have an arrangement ofcompressor rotor blades 22 which project radially outwards from arotatable drum or disk 26 linked to hubs 27 of the high-pressure turbine16 or the intermediate-pressure turbine 17, respectively.

The turbine sections 16, 17, 18 have similar stages, including anarrangement of fixed stator vanes 23 projecting radially inwards fromthe casing 21 into the annular flow duct through the turbines 16, 17,18, and a subsequent arrangement of turbine blades 24 projectingoutwards from a rotatable hub 27. The compressor drum or compressor disk26 and the blades 22 arranged thereon, as well as the turbine rotor hub27 and the turbine rotor blades 24 arranged thereon rotate about theengine axis 1 during operation.

FIG. 2 shows a simplified sectional view according to the state of theart, showing a combustion chamber wall 29 provided with severalimpingement cooling holes 31. Combustion chamber tiles 30 provided witheffusion holes 32 are arranged at a distance to the combustion chamber29. The combustion chamber tiles 30 are fastened in the usual mannerusing bolts 33 to the combustion chamber wall 29 (tile carrier) suchthat an interspace 34 is obtained through which the cooling air can flowin the manner shown from the impingement cooling holes 31 to theeffusion holes 32.

FIGS. 3 and 4 each show the assignment of impingement cooling holes 31to effusion holes 32. The impingement cooling holes 31 are illustratedas stars while the effusion holes are shown as ellipses. This embodimentdoes not have to conform to the actual hole design; it was selected onlyto make the figures clear.

FIG. 3 shows a design arrangement provided according to a designdrawing, where it can be seen that the impingement cooling holes 31 andthe effusion holes 32 are arranged on a linear grid and are at an equaldistance from one another in terms of their center points.

FIG. 4 shows the arrangement according to FIG. 3 in the actualembodiment with component tolerances and assembly tolerances. It can beseen here that the impingement cooling holes 31 are displaced relativeto the arrangement of the effusion holes 32 such that the impingementcooling holes 31 partially overlap the effusion holes 32, with theresult that sufficient impingement cooling cannot take place.Furthermore, the flow through the effusion holes 32 is altered by thedirectly impinging cooling air.

FIG. 5 shows an exemplary embodiment in accordance with the invention asper the inventive method. The result of this is that the impingementcooling holes 31 are provided in an arrangement differing from the evenarrangement of the effusion holes 32. In accordance with the invention,they are assigned such that in the actual arrangement shown in FIG. 6,with the component tolerance and the assembly tolerance taken intoconsideration, all or almost all impingement cooling holes 31 are placedsuch that the airflow impinges not at all or only negligibly on theeffusion holes 32. This results in the advantages described inaccordance with the invention, so that dependable and operationally safecooling is assured.

LIST OF REFERENCE NUMERALS

-   1 Engine axis-   10 Gas-turbine engine/core engine-   11 Air inlet-   12 Fan-   13 Intermediate-pressure compressor (compressor)-   14 High-pressure compressor-   15 Combustion chamber-   16 High-pressure turbine-   17 Intermediate-pressure turbine-   18 Low-pressure turbine-   19 Exhaust nozzle-   20 Guide vanes-   21 Engine casing-   22 Compressor rotor blades-   23 Stator vanes-   24 Turbine blades-   26 Compressor drum or disk-   27 Turbine rotor hub-   28 Exhaust cone-   29 Combustion chamber wall-   30 Combustion chamber tile-   31 Impingement cooling hole-   32 Effusion hole-   33 Bolt-   34 Interspace

What is claimed is:
 1. Method for the arrangement of effusion holes andimpingement cooling holes in a combustion chamber wall and in combustionchamber tiles of a gas turbine, with the combustion chamber having acombustion chamber wall provided with impingement cooling holes andcombustion chamber tiles, which are arranged at a distance from thecombustion chamber wall and provided with effusion holes, characterizedin that the method includes the following process steps: 1.) Stipulationof the maximum permitted number of matches, where an impingement poolinghole axis matches an effusion hole center point at a distance y, and ofthe minimum spacing between the matches. 2.) Selection of the patternfor the effusion holes. 3.) Stipulation of the diameter of the effusionholes. 4.) Calculation of the dimensions of the basic cell for theeffusion holes, such that all holes provided fit into the surface to becooled. 5.) Distribution of the effusion holes in the surface to becooled in accordance with the selections made under
 2. and
 3. 6.)Selection of the pattern for the impingement cooling holes. 7.)Stipulation of the diameter of the impingement cooling holes. 8.)Calculation of the dimensions of the basic cell, such that allimpingement cooling holes provided fit into the surface to be cooled.9.) Selection of the alignment of the basic cell for the impingementcooling holes. 10.) Distribution of the impingement cooling holes inaccordance with the selections made under
 6. and
 7. 11.) Checking of thenumber of matches and their spacing from one another, taking intoaccount the component and assembly tolerances. 12.) Comparison with thepermitted number and their minimum spacing. 13.) If the qualityrequirements are not met: a) First select another alignment of the basiccell of the impingement cooling holes and return to
 10. b) If this doesnot succeed, chose another diameter of the impingement cooling holes andreturn to
 8. c) If this does not succeed, chose another pattern and/oranother basic cell of the impingement cooling holes and return to
 6. d)If this does not succeed, chose another effusion hole diameter andreturn to
 4. e) If this does not succeed, chose another effusion holepattern and return to
 3. f) If this does not succeed, check the inputdata from the total of the geometric surfaces of all effusion holes, thetotal of the geometric surfaces of all impingement cooling holes and thesurface to be cooled. g) If this does not succeed. change the qualityrequirements.
 2. Combustion chamber wall of a gas turbine, which atleast on one part of the combustion chamber wall is provided with atwo-layer cooling system and designed in accordance with the method ofclaim
 1. 3. Combustion chamber wall in accordance with claim 2,characterized in that at least on one part of the combustion chamberwall the impingement cooling holes are distributed according to adifferent rule than that for the effusion holes, while avoiding a fixedgeometric relationship between the impingement cooling holes and theeffusion holes.
 4. Combustion chamber wall in accordance with claim 3,characterized in that at least on one part of the combustion chamberwall no even-numbered multiples of the number of impingement coolingholes are provided for the number of effusion holes.